The present invention is an absorbent article for personal care, particularly feminine hygiene products, which can accept liquid, distribute it and retain it.
Personal care articles include such items as diapers, training pants, feminine hygiene products such as sanitary napkins, panty-liners and tampons, incontinence garments and devices, bandages and the like. The most basic design of all such articles typically includes a bodyside liner, an outercover (also referred to as a baffle) and an absorbent core disposed between the bodyside liner and the outercover.
Personal care products must accept fluids quickly and hold them to reduce the possibility of leakage outside the product. The product must be flexible and have a pleasing feel on the skin, and even after liquid insult, must not become tight or bind the user. Unfortunately, while previous products have met many of these criteria to varying degrees, a number have not.
In particular, feminine hygiene products for longer term (i.e. overnight) usage are subject to higher and more variable flow rates and fluid loads than are those intended for regular or shorter term usage. Products for overnight usage, therefore, must have the ability to absorb and contain continuous and light flow as well as gushes and sudden heavy flow over the life of the product. It has been found that continuous flow insults in feminine hygiene products average 1 ml/hr, but may be higher, and are not literally continuous or constant, but rather variable in rate and may even pause during a cycle. xe2x80x9cGush flowxe2x80x9d is defined as a sudden heavy flow condition and occurs at flow rates of up to 1 ml/sec. During a gush, 1-5 ml of fluid is released from the body onto the product. The term xe2x80x9ccontinuous flowxe2x80x9d is used to define any flow which falls outside of the definition of gush flow.
Combining continuous and gush flow conditions results in variable flow. Essentially, xe2x80x9cvariable flowxe2x80x9d is defined as continuous flow with intermittent gush flow occurrences. FIG. 1 is a graph which illustrates the differences between variable flow (diamonds) and continuous flow (squares) over the life of a single product where flow rate volume is on the y-axis in g/hr and time is on the x-axis in hours. This problem of handling gush and continuous flows is termed variable flow management and is defined as the ability to absorb and contain continuous and light flow (1-2 ml/hr) as well as multiple gushes or sudden heavy flow insults (1 ml/sec with a total volume of 1-5 ml) over the life of the product. It is obvious that the challenge of variable flow management is more difficult as the wear time of the product is lengthened, such as in overnight use conditions.
Many feminine care cover materials have low z-directional conductivity, low surface energy, low void volume, and provide little separation between the absorbent core and the user due to their two dimensional structure. Consequently, these covers result in slow and incomplete intake, high rewet, and large surface stains. In addition, typical intake or acquisition layers are low density, high void volume structures which are ideal for fast fluid intake, but because these structures typically have low capillarity, fluid is not adequately desorbed from the cover material, resulting in smearing and surface wetness. Materials which enhance cover desorption are typically high density, high capillarity materials, but because these materials have low void volume and low z-directional permeability, they inherently retard fluid intake.
There remains a need to address variable flow management from the overall product form standpoint, developing a system in which the components are optimized to function together. In such a system, the liner is designed to promote rapid intake and remain clean and dry, there is an intake/distribution material which has the void volume necessary for fast intake and the high capillarity desired for sufficient cover desorption while maintaining an appropriate capillary structure for fluid intake/distribution and the absorbent (retention) layer accepts fluids at the appropriate speed.
An objective of this invention is, therefore, to provide an overall design for a feminine hygiene product, particularly for overnight use, to manage a wide variety of flow conditions including sudden heavy flow insults, or gushes.
The objects of the invention are achieved by a creped spunbond nonwoven fabric for use as the liner or outer cover, an improved absorbent core using a co-apertured airlaid fabric layer and spunbond nonwoven fabric transfer delay layer, over a fluff retention layer. Combining these improvements into an integrated absorbent system allows the successful achievement of variable flow management and a successful balance between intake and cover desorption properties. The result is improved multiple intake performance and a clean and dry cover surface during use. The material technology developments regarding variable flow management focus on attaining the proper material structure and property balance necessary to achieve fast intake and improve cover desorption, cover staining, and rewet characteristics. These functional properties are provided through improved material technologies and product construction.